Apparatus for embossing a web

ABSTRACT

An apparatus for embossing a web having a static gas pressure plenum and a forming structure disposed in contact to the static gas pressure plenum. The static gas pressure plenum provides a static gas pressure of from about 0.1 MPa to about 25 MPa.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. patent application Ser. No.13/045,991 which claims the benefit of U.S. Provisional Application No.61/313,122, filed Mar. 11, 2010. All documents are incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to an apparatus for embossing a web.

BACKGROUND OF THE INVENTION

Web materials, such as thermoplastic films, have a variety of usesincluding component materials of absorbent articles (such as topsheetsand backsheets), packaging (such as flow wrap, shrink wrap, andpolybags), trash bags, food wrap, dental floss, wipes, electroniccomponents, and the like. For many of these uses of web materials, itcan be beneficial for the web material to have a textured surface, whichcan provide the surface of the web material with a desirable feel,visual impression, and/or audible impression.

Polymeric webs exhibiting a soft and silky tactile impression can bemade via a vacuum forming process or a hydroforming process. With atypical vacuum forming process, a precursor web is heated and placedover a forming structure. Then a vacuum forces the precursor web toconform to the texture of the forming structure. The resulting polymericweb has texture that can provide a soft and silky tactile impression,depending upon the texture of the forming structure and degree ofconformation. While a vacuum forming process can be suitable for makinga soft and silky polymeric web, a vacuum forming process is typicallylimited with respect to the amount of pressure capable of being exertedonto a precursor web. As a result, it is usually required to heat aprecursor film to significantly soften or melt the precursor film priorto placement on the forming structure in order to vacuum form theprecursor film to the forming structure. A vacuum forming process istherefore an inefficient process in terms of how fast the process can beperformed due to the heating step and the limited pressures generated bythe process.

With a typical hydroforming process, a precursor web is placed over aforming structure and high pressure and high temperature water jetsforce the precursor web to conform to the texture of the formingstructure. The resulting polymeric web can have texture that can providea soft and silky tactile impression, depending upon the texture of theforming structure. A hydroforming process, although capable of producingsoft and silky polymeric webs, is typically a costly and inefficientprocess involving the use of high pressure and high temperature waterjets and subsequent drying steps, including dewatering steps.

Embossing is a process that typically involves the act of mechanicallyworking a substrate to cause the substrate to conform under pressure tothe depths and contours of a pattern engraved or otherwise formed on anembossing roll. It is widely used in the production of consumer goods.Manufacturers use the embossing process to impart a texture or reliefpattern into products made of textiles, paper, synthetic materials,plastic materials, metals, and wood. When the substrate is athermoplastic, permanent strain remaining in the substrate can provide atexture and/or visual that remains with the surface of the substrate.

Embossing processes have been used to provide texture to polymericfilms. However, such embossing processes typically require extruding amolten resin onto a forming structure or heating a precursor web beforeplacement onto a forming structure and then embossing to produce anembossed web. The embossed web is then cooled, typically by cooling theembossing rolls or plates used to emboss the heated precursor web ormolten resin. The cooling step is often utilized to set the texture inthe embossed web. However, these heating and cooling steps addundesirable cost and inefficiency, as well as complexity, to theprocess. In addition, such embossing processes typically involverelatively large dwell times, which can result in slow, inefficientprocesses.

It is also typically difficult to impart relatively small scale textureto precursor webs using conventional embossing processes. Furthermore,typical embossing processes tend to produce embossed webs havingrelatively uniform thickness throughout the web.

Despite the knowledge in the art, there remains a desire to develop amore efficient and effective apparatus for making embossed webs.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus for embossing a webcomprising an area containing a static gas pressure plenum and one ormore forming structures. The static gas pressure plenum provides astatic gas pressure of from about 0.1 MPa to about 25 MPa.

The present invention also relates to an apparatus for embossing a webcomprising a pressure hood, a forming structure disposed adjacent saidpressure hood, a gap between said pressure hood and said formingstructure defining a static gas pressure plenum, an infeed sealingroller contacting said forming structure, thereby forming an infeed nip,and an outfeed sealing roller contacting said forming structure, therebyforming an outfeed nip.

The present invention also relates to an apparatus for embossing a webcomprising one or more compliant rolls and one or more formingstructures. The one or more forming structures and the one or morecompliant rolls are in contact forming a high pressure zone defining astatic gas pressure plenum.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an apparatus for embossing a web in accordancewith an embodiment of the disclosure.

FIG. 2 is a perspective view of an apparatus for embossing a web inaccordance with an embodiment of the disclosure mounted in a frame witha side plate of the frame removed.

FIG. 3 is a side view of an apparatus for embossing a web in accordancewith an embodiment of the disclosure.

FIG. 4 is a perspective view of a pressure hood of an apparatus forembossing a web with the forming structure and one infeed idler rollremoved in accordance with an embodiment of the disclosure with theforming structure roll removed.

FIG. 5 is a cross-sectional view of an apparatus for embossing a web inaccordance with an embodiment of the disclosure.

FIG. 6 is a cross-sectional view of a sealing roller and formingstructure interface of an apparatus for embossing a web in accordancewith an embodiment of the disclosure.

FIG. 7 is a cross-sectional view of a forming structure, pressure hood,and stationary sealing plate of an apparatus for embossing a web inaccordance with an embodiment of the disclosure.

FIG. 8 is a schematic of an apparatus for embossing a web in accordancewith an embodiment of the disclosure.

FIG. 9 is a perspective view of an apparatus for embossing a web inaccordance with an embodiment of the disclosure.

FIG. 10 is a schematic of an apparatus for embossing a web in accordancewith an embodiment of the disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The apparatus 36 of the present invention is utilized to emboss aprecursor web 34 of material in order to impart a texture and/or patterninto the web of material. The apparatus 36 of the present inventionincludes a forming structure 10 and a static gas pressure plenum 40. Thestatic gas pressure plenum 40 may be formed by a pressure hood 38 or byone or more forming structures 10 and one or more compliant rolls 80 incontact enclosing a high pressure zone 46.

The apparatus 36 as shown in FIG. 1 includes a forming structure 10, aninfeed 50 and outfeed 52 sealing roller, and a pressure hood 38. Theforming structure 10 can be any suitable forming structure 10 designedto impart a texture and/or pattern into a precursor web 34 of materialto form an embossed web. The pressure hood 38 includes a high pressuregas inlet 42. The gap 44 between the forming structure 10 and thepressure hood 38 defines a static gas pressure plenum 40.

The apparatus 36 as shown in FIG. 2 includes a forming structure 10, aninfeed sealing roller 50, idler rolls 70, 72, web sealing belts 64,spring loaded mounts 56, a sealing plate 60, and a pressure hood 38.

The apparatus 36 as shown in FIG. 3 includes a forming structure 10, apressure hood 38, an infeed sealing roller 50, spring loaded mounts 56,web sealing belts 64, an idler rolls 70, and a high pressure gas inlet42 located in the pressure hood 38. The high pressure gas inlet 42provides a static gas pressure of from about 0.1 MPa to about 25 MPa tothe static gas pressure plenum 40.

The pressure hood 38 as shown in FIG. 4 includes infeed 50 and outfeed52 sealing rollers, web sealing belts 64, an idler roll 70, and sealingplates 60.

The apparatus 36 as shown in FIG. 5 includes a forming structure 10, apressure hood 38, a high pressure gas inlet 42, an infeed sealing roller50, a spring loaded mount 56 that impacts upon the infeed sealing roller50, a web sealing belt 64, and an idler roll 70.

The apparatus 36 as shown in FIG. 6 represents a cross-sectional view ofa sealing roller 50 and forming structure 10 interface. The crosssectional view includes a spring loaded mount 56 and a web sealing belt64.

The apparatus 36 as shown in FIG. 7 represents a cross-sectional view ofa forming structure 10, a pressure hood 38, and a stationary sealingplate 60. The cross-sectional view includes a web sealing belt 64.

The schematic as shown in FIG. 8 represents an embodiment including twoforming structures 10, two compliant rolls 80, a framing plate 62, ahigh pressure gas inlet 42 that provides a static gas pressure of fromabout 0.1 MPa to about 25 MPa to the static gas pressure plenum 40, andinlet and outlet idler rolls 70, 72.

The apparatus 36 as shown in FIG. 9 includes two forming structure 10,two compliant rolls 80, eight sealing plates 60, two framing plates 62,and a high pressure gas inlet 42.

The schematic as shown in FIG. 10 represents an embodiment includingthree forming structures 10, three compliant rolls 80, two framingplates 62, two high pressure gas inlets 42 that provide static gaspressure of from about 0.1 MPa to about 25 MPa to each static gaspressure plenum 40. The forming structures 10 may differ in pattern andmaterial. The two high pressure gas inlets 42 can provide differentpressures between 0.1 MPa to about 25 MPa to each static gas pressureplenum 40 such that the pressures vary in each high pressure zone 46.

The forming structure 10 can be any suitable forming structure 10designed to impart a texture and/or pattern into a precursor web 34 ofmaterial to form an embossed web. The forming structures 10 aretypically in the form of a roll or sleeve. In an embodiment, formingstructure 10 is in the form of a belt. The forming structure 10 may bemade from any suitable material, such as, for example, aluminum, nickel,copper, low carbon steel, stainless steel, or tungsten carbide. Theforming structure 10 can also be made from plastics, such as, forexample, Delrin (Acetal Resin), Lexan, Nylon, PVC, or any other plasticthat exhibits high stiffness, low friction, good dimensional stability,and is machinable.

In one embodiment, the forming structure 10 comprises a plurality ofdiscrete apertures, discrete depressions, or combinations thereof. Sucha forming structure 10 is described in more detail in U.S. PublicationNo. 2010-0230866 A1, filed Mar. 11, 2010.

In one embodiment, the forming structure 10 comprises a plurality ofdiscrete protruded elements. Such a forming structure 10 is described inmore detail in U.S. Publication No. 2010-0230867 A1, filed Mar. 11,2010.

In one embodiment, the forming structure 10 comprises a plurality ofdiscrete apertures, discrete depressions, discrete protruded elements orcombinations thereof.

In an embodiment, the compliant rolls 80 are made of urethane.Alternatively, the compliant rolls 80 may be made of any suitablematerial, such as, for example, polyurethane, natural rubber, and gumrubber. The compliant rolls 80 may also vary in diameter. Other suitablecompliant materials are described in more detail in U.S. Publication No.2010-0230858 A1, filed Mar. 11, 2010.

A high pressure gas inlet 42 provides a source of high pressure gas tothe static gas pressure plenum 40. The gas can be air, nitrogen, carbondioxide, and the like, or combinations thereof. The static gas pressureplenum 40 exerts a pressure on the precursor web 34. Under static gaspressure conditions, there is no velocity and density impinging upon theunembossed precursor web 34 as with a velocity pressure source such asan air knife Rather, a static high gas pressure is maintained whichcreates a pressure differential across the precursor web, between thestatic gas pressure plenum 40 facing surface of the precursor web 34 andthe forming structure 10 facing surface of the precursor web 34.

A pressure of about 100 psi is provided by the static gas pressureplenum 40. The pressure is sufficient to force the precursor web 34,which is positioned between the forming structure 10 and static gaspressure plenum 40, into the discrete apertures or depressions, or aboutthe discrete protruded elements, of the forming structure 10 to form anembossed web. In general, the pressure provided between the formingstructure 10 and static gas pressure plenum 40 is about 0.1 MPa to about25 MPa, about 1 MPa to about 20 MPa, about 0.5 MPa to about 10 MPa,about 7 MPa to about 25 MPa, about 10 MPa to about 25 MPa, or about 0.5MPa to about 5 MPa.

The pressure provided by the static gas pressure plenum 40 allows forimproved dwell times of the precursor web 34 on the forming structure10. In an embodiment, the pressure is typically applied to the precursorweb 34 for a dwell time of less than about 5 seconds, less than about 1second, less than about 0.5 second, less than about 0.1 second, lessthan about 0.01 second, or less than about 0.005 second. For example,the dwell time can be about 0.5 milliseconds to about 50 milliseconds.Even with such relatively short dwell times, embossed webs can beproduced with desirable structural features described herein. As aresult, the process of the disclosure enables high speed production ofembossed webs.

The precursor web 34 can be fed between the forming structure 10 and thestatic gas pressure plenum 40 at a rate of at least about 0.01 metersper second, at least about 1 meter per second, at least about 5 metersper second, or at least about 10 meters per second. Other suitable ratesinclude, for example, at least about 0.01, 0.05, 0.1, 0.5, 1, 2, 3, 4,5, 6, 7, 8, 9, or 10 meters per second.

The apparatus 36 can further include a sealing plate 60 disposed on eachend of the forming structure roll 10 and compliant roll 80. The sealingplate 60 is a stationary member that maintains a lateral seal againstthe edges of the forming structure roll 10 and compliant roll 80.

The apparatus can further comprise infeed 70 and outfeed 72 idlerrollers. In an embodiment, the infeed 70 and outfeed 72 idler rollersare adjustable in relation to the forming structure.

Web sealing belts 64 can be included to seal the sides of the precursorweb 34 against the forming structure 10 as it enters the infeed nip, andas it exits the outfeed nip, to ensure that a pressure difference acrossthe web is maintained so that the high pressure gas can impact the web.Web sealing belts 64 can also be included to seal the sides of theprecursor web 34 against the one or more forming structures 10 when thehigh pressure zone 46 is defined by one or more forming structures 10and one or more compliant rolls 80.

The web sealing belts 64 can fit into recessed areas at each end of theinfeed 70 and outfeed 72 idler rolls, as shown in FIGS. 3 and 4. The websealing belts 64 can further fit into recessed areas at each end of theforming structure roll 10 as shown in FIGS. 6 and 7.

In an embodiment, vacuum can be used on the forming structure 10. Thevacuum can aid in removing trapped air under the web and avoidingpneumatic pressure under the web as the film is conformed to the formingstructure 10. The vacuum can enhance the pressure differential acrossthe web. The vacuum can be applied in any suitable manner, such as, forexample, by using vent holes that are smaller in diameter than thethickness of the precursor web 34 or by using apertures. Alternatively,the vacuum can also be applied by using a porous forming structure 10.In an embodiment, vacuum can be applied inside a forming structure 10.

In an embodiment, heat is used during the embossing process. Heat can beprovided in any suitable manner, such as, for example, by heating thehigh pressure gas, heating the forming structure 10, pre-heating theprecursor web 34, heating the compliant rolls 80, using localized heatsuch as, for example, inserting a small cartridge heater inside theforming structure 10, or radiant heat as described in Gray (U.S. Pat.No. 6,780,372). Heat can also be provided by any combination of thesources that provide heat.

The precursor web 34 that is embossed by the apparatus of the presentinvention can be comprised of a wide variety of materials. Suitableprecursor webs 34 include synthetic material, metallic material,biological material (in particular, animal-derived material), orcombinations thereof. In one embodiment, the precursor web 34 is athermoplastic film, preferably comprised of polyethylene, polypropylene,or blends thereof. Other suitable precursor webs are described in detailin U.S. Publication No. 2010-0230866 A1, filed Mar. 11, 2010 and U.S.Publication No. 2010-0230867 A1, filed Mar. 11, 2010.

The apparatus 36 of the present invention can be utilized in processesfor making embossed webs, such as those processes described in detail inU.S. Publication No. 2010-0230866 A1, filed Mar. 11, 2010 and U.S.Publication No. 2010-0230867 A1, filed Mar. 11, 2010.

An embodiment of the apparatus 36 can further include infeed 50 andoutfeed 52 sealing rollers which each contact the forming structure todefine an infeed nip and an outfeed nip. The infeed 50 and outfeed 52sealing rollers are utilized to enhance the seal of the static gaspressure plenum 40 to maintain sufficient gas pressure in the static gaspressure plenum 40 and also minimize air leakage.

In an embodiment, the infeed 50 and outfeed 52 sealing rollers can alsobe utilized to further force the precursor web 34 against the formingstructure 10 in order to enhance the formation of texture and/or patternin the embossed web and also minimize air leakage. Spring-loaded mounts56 or other similar mounts can be utilized to further force the infeed50 and/or outfeed 52 sealing rollers against the forming structure 10 inorder to increase the amount of pressure applied to the precursor web 34as it enters the infeed nip or outfeed nip. To enhance the formation oftexture and/or pattern in the embossed webs, the infeed nip and/oroutfeed nip can exhibit pressures ranging from about 0.3 MPa to about68.9 MPa, from about 0.7 MPa to about 34.5 MPa, or from about 0.7 MPa toabout 24.1 MPa.

The infeed 50 and/or outfeed 52 sealing rollers can comprise a compliantmaterial. Suitable compliant materials include elastomers, felts,liquid-filled bladders, and combinations thereof. Other suitablecompliant materials are described in detail in U.S. Publication No.2010-0230858 A1, filed Mar. 11, 2010. The compliant material can have aShore A hardness of from about 30 to about 80 durometer. The thicknessof the compliant material covering the rigid material will typically beno greater than about 26 mm, from about 1 mm to about 26 mm, or fromabout 1 mm to about 7 mm.

In an embodiment, the apparatus 36 can include a pressure hood 38. A gap44 between the pressure hood 38 adjacent the precursor web 34, which isfed between the pressure hood 38 and the forming structure 10, definesthe static gas pressure plenum 40. The static gas pressure plenum 40 isutilized to provide a force against a precursor web 34 to force theprecursor web 34 into the apertures or depressions, and/or to conformthe precursor web to the discrete protruded elements, of the formingstructure 10. The gap 44 between the pressure hood 38 and the formingstructure 10 can be from about 0.5 mm to about 50 mm or from about 1 mmto about 4 mm The pressure hood 38 can include at least one highpressure gas inlet 42 allowing high pressure gas to enter the gap 44between the pressure hood 38 and the forming structure 10 creating thestatic pressure conditions in the gap 44 between the pressure hood 38and the forming structure 10.

In an embodiment, the sealing plate 60 maintains a lateral seal againstthe edges of the forming structure roll 10 and the pressure hood 38.

In an embodiment, the pressure hood 38 is wider than the precursor web34, which can enhance the seal formed with the pressure hood 38. Thepressure differential is sufficient to force the precursor web 34 intothe apertures or depressions, or to conform the precursor web 34 to thediscrete protruded elements, of the forming structure 10. The pressuredifferential can be enhanced, for example, by applying a vacuum on theforming structure 10 facing surface of the precursor web 34.

In an embodiment, the static gas pressure plenum 40 may be defined by ahigh pressure zone 46 created between one or more forming structures 10and one or more compliant rolls 80. The volume of the high pressure zone46 created between the one or more forming structures 10 and one or morecompliant rolls 80 can vary according to the diameter of the formingstructures 10 and compliant rolls 80. Any suitable number of formingstructures 10 can be used, such as, for example, one, two, three, four,five, six, eight, ten. Any suitable number of compliant rolls 80 can beused, such as, for example, one, two, three, four, five, six, eight,ten. The total number of forming rolls 10 and compliant rolls 80 shouldbe an even number greater than or equal to four.

In an embodiment, the static gas pressure plenum 40 defined by the oneor more forming structures 10 and one or more compliant rolls 80 canprovide force against one or more than one forming structure 10simultaneously. An embodiment with multiple forming structures 10 andone or more compliant rolls 80 can allow for multiple embossings on thesame web using the same static gas pressure plenum 40. An embodimentwith multiple forming structures 10 and one or more compliant rolls 80can have variations in the forming structure, such as, for example, thematerial from which the individual forming structures 10 are made,forming different shapes, different sizes, different area densities,and/or embossing patterns created by the discrete apertures, discretedepressions, discrete protruded elements or combinations thereof of theindividual forming structure 10.

In an embodiment, defined by the one or more forming structures 10 andone or more compliant rolls 80, the embodiment can have different staticgas pressure plenums 40. The one or more forming structures 10 and theone or more compliant rolls 80 in contact create two or more separatehigh pressure zones 46 each defining a different the static gas pressureplenum 40.

Each static gas pressure plenum 40 can provide force against one oremore than one forming structure 10 in the high pressure zone 46simultaneously. An embodiment with multiple forming structures 10 andone or more compliant rolls 80 can allow for multiple embossings on thesame web using different static gas pressure plenums 40.

The static gas pressure plenum 40 of an embodiment defined by one ormore forming structures 10 and one or more compliant rolls 80 can beaffected by aspects of the rolls, such as, for example, the diameter ofthe compliant rolls 80.

In an embodiment, more than one sealing plate 60 serves to maintain thestatic gas pressure plenum in the high pressure zone 46.

The apparatus 36 can include a sealing framing plate 62 disposed on eachend of the apparatus 36. The framing plate 62 can include the more thanone sealing plate 60 in an embodiment comprising one or more formingstructures 10 and one or more compliant rolls 80.

In an embodiment, the framing plate 62 includes the high pressure gasinlet 42.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

All documents cited in the Detailed Description of the Invention are, inrelevant part, incorporated herein by reference; the citation of anydocument is not to be construed as an admission that it is prior artwith respect to the present invention. To the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. An apparatus for embossing a web comprising: oneor more compliant rolls; and one or more forming structures; wherein theone or more forming structures and the one or more compliant rolls arein contact forming a high pressure zone defining a static gas pressureplenum.
 2. The apparatus of claim 1, wherein said static gas pressureplenum provides a static gas pressure of from about 0.1 MPa to about 25MPa.
 3. The apparatus of claim 1, wherein said static gas pressureplenum provides a static gas pressure of from about 1 MPa to about 25MPa.
 4. The apparatus of claim 1, wherein said static gas pressureplenum is defined by contacting at least four in total of one or more ofsaid forming structures with the one or more said compliant rolls. 5.The apparatus of claim 1, wherein the one or more forming structures andthe one or more compliant rolls in contact create two or more separatehigh pressure zones each defining a different said gas pressure plenum.6. The apparatus of claim 1, wherein the one or more forming structurescomprises a vacuum within a forming structure.
 7. The apparatus of claim1, wherein the one or more forming structures comprise protrudedelements.
 8. The apparatus of claim 1, wherein said apparatus furthercomprises an infeed idler roll and an outfeed idler roll, wherein theinfeed idler roller and the outfeed idler roller are adjustable inrelation to the forming structures.
 9. The apparatus of claim 8, whereinsaid infeed sealing roller and said outfeed sealing roller each comprisea compliant material, wherein the compliant material is a materialhaving a Shore A hardness between 30 and 80 durometer.